Many household and commercial appliances have combustion chambers where natural gas, propane, or oil or some other fuel may be burned. For example, boilers and furnaces used for creating hot water and/or heating include a combustion chamber where fuel is burned to provide heating for the hot water or hot air. Like any other mechanical device, these combustion appliances from time to time may require maintenance or cleaning.
In order to provide access to the combustion chamber for maintenance or cleaning, these appliances are often equipped with a combustion chamber door. The door may be opened to thereby provide access to the combustion chamber. For a variety of reasons it is important that the combustion chamber door is securely closed whenever combustion occurs within the combustion chamber.
Many appliances having combustion chambers are not always burning fuel within the combustion chamber. For example, a boiler may only burn fuel in the combustion chamber when a thermostat or other controller sends a signal to the boiler requesting it produce hot water. At other times the combustion chamber may be idle. When the boiler gets a call for heat, or is signaled to produced hot water, it may provide fuel flow to the combustion chamber and an electrical charge may ignite the fuel causing the combustion to occur. Accordingly, during operation of the appliance there will be times when there is fuel burning in the combustion chamber and other times when there is not fuel burning in the combustion chamber.
As a result of the on-again, off-again fuel burning occurring in the combustion chamber, a potential problem may arise when someone desiring to access the combustion chamber notices that there is no combustion occurring in the combustion chamber and opens the door accessesing the combustion chamber in order to clean or provide maintenance to the combustion chamber. During the time when the door is opened and the combustion chamber is exposed, if the appliance were not properly shut off or set for maintenance operations, the appliance could receive a call to produce heat and initiate the ignition sequence. The ignition sequence could provide fuel flow and an electrical signal to provide a spark to ignite the fuel in the combustion chamber and cause combustion in the combustion chamber. As previously mentioned, it is undesirable for the combustion door to be open when fuel is burning in the combustion chamber.
Accordingly, there is a need in the art for a method and apparatus that disables the combustion sequence from occurring when the combustion door is open. There is also a need for a method and apparatus that will not allow fuel to ignite in the combustion chamber when the combustion chamber access door is open.